This is a live Arabidopsis inflorescence with young flower buds developing at the periphery. Cell walls have been stained with propidium iodide (grey). Fluorescent reporters were used to monitor the expression of the APETALA3 (AP3, green) and SUPERMAN (SUP, red) genes. AP3 is required for the development of stamens (the male organs), while SUP establishes the boundary between the male and female part of the flower. This picture was acquired using live confocal imaging, which allows us to describe the expression of several genes in both space and time, in the same live biological samples, with a precise cellular resolution. It finally allows us to understand a question that has been elusive for 25 years: how the male/female boundary is established during the formation of the flower. My research aims at understanding how flower buds are patterned as they form.